The invention relates to a device for gripping and holding substrates with one or several substrate holders arranged in a vacuum chamber and one or several displaceably arranged grippers, which can be displaced into a first position through the action of an operating pressure or against the action of a spring, and into a second position through the action of a diaphragm, which can be exposed to a pneumatic pressure P.sub.a and/or an operating element cooperating with it, wherein the substrate is held in the one position and in the second position the substrate is released for being further transported.
A device for gripping and holding a disklike substrate is disclosed in German Utility Model DE-GM 93 07 263.5. This device comprises a number of circularly arranged grippers and an elastic diaphragm which is disposed in a pressure-proof housing that has an opening. Different pressures can be established on the front and back sides of the diaphragm, and the diaphragm may be arranged such that at a differential pressure, a deflection of the diaphragm out of its position of repose takes place, while at a pressure equilibrium the diaphragm returns to its position of repose via a compression spring.
The differential pressure at the diaphragm is generated in that a bell-shaped housing, which is provided with a central bore, is disposed on one side of the diaphragm. A pressure chamber is formed between the end of the bore of the bell-shaped housing and the surface of the diaphragm. The bore provided in the bell-shaped housing is provided via a pneumatic line with an external pump whose sole function is to establish a differential pressure on the surface of the diaphragm, relative to the vacuum pressure provided in the chamber beneath, so that by imposition of pressure on the diaphragm and by means of an adjusting part adjoining the diaphragm, the gripper arm can be adjusted out of its position that holds the substrate into a further position in which the gripper or grippers release the substrate. Such an apparatus is complicated and expensive, since a separate pump is required to generate this differential pressure, and the diaphragm must be sealed off from the pressure in the vacuum chamber so that the requisite pressure can be generated on the back side of the diaphragm. Moreover, such an arrangement is highly vulnerable to malfunction, since the additionally required pump operates entirely uncoupled from the other pumps to generate the vacuum pressure in the vacuum chamber, so that a completely exact adaptation to the operating process for adjusting the diaphragm and removing the substrate is impossible. Overall, such an apparatus works relatively slowly, since the release of the substrate cannot occur until the necessary system pressure downstream of the diaphragm has built up via the independent pump. The compressed-air supply line must be disposed flexibly relative to the holding mechanism.